I've come to the conclusion that I'm just not crazy about the 2 band Bart preamp (NTBT) on my Ibanez GWB1 (fretless 5 string).

I like 3 band. I like being able to boost mids. Currently I'm boosting mids on my amp. Do-able, but I like having the sound I want dial-able from the bass.

So - Bart NTMB or Aguilar OPB3? Or other?
Or don't mod the bass at all (a 3 band pre will require drilling an additional hole).

Your thoughts, brothers and sisters of the low end?

FWIW, I was in a similar situation - 5 string fretless w/ Bart NTBT - and went on a similar quest for tone nirvana. I went with the ACG filter pre and have been very happy. :hyper:
My alternate top choices included the Bart NTMB. I also found I could get the Bart NTMB in a 4 knob form - my bass is drilled for 4.
Much of my research indicated managing the mids is the secret to a great fretless sound.
Good luck with your quest. :D

I don't have a ton of experience with the other preamps that you mentioned, but I have owned four basses with the bart 3 band, and I have always thought is was very nice. Two of those basses were fretless.

I especially liked the feature on the Roscoe that has the push/pull to select between 300 and 800 for the mid sweep. If you have a little extra for that mod, you'll love it.

Also, I am certain you can come up with the right combination of stacked pots to avoid drilling another hole. It might cost a you a little, but worth it. If you ever decide to sell the bass, you won't get you money back on the preamp mod. You're better off switching back to stock and selling it seperate.